I did hear about that Tulsa is alittle farther than I want to go. Michigan was a stretch.

 

I guess I don't understand the part about mine want to go straight up and down?

If I got heim joint bars, would I put them in the factory location or the lower holes where the lift are were. If i put them back in the stock holes I assume it will lengthen and lower my instant center. Is that good? It 60's ok now I don't want to make it any worse.

 

Can you explain this more or point me in a direction to find more info?

 

It's simple, they are 2 unequal length control arms at 2 different angles and attachment angles. It's why the factory used such large bushings in the ca's. It's been common knowledge for about 25 years that southside bars and fox mustangs are a bad combination. They earned the nickname torque box killers for a reason. I got some of this geometry info from Kevins years ago on corral and our various conversations over the years. If you take tge springs out and support the rear with a floor jack and body with stands, you can raise and lower the rear axle and observe the travel of upper and lower arms. It's why stiff urethane bushings make the rear end 'stick' in a certain position when you lower it down off a rack. I have worked on foxes since 94, so this is all common knowledge for me gleaned from years of experience and reading. Spherical ends on at least one end of upper and lower, allow the rear axle to have a very smooth range of motion.

 

So, it's a bushing issue, not the bar geometry that causes the problem? That makes more sense. It seems that any triangulated 4 link will bind with a firm poly bushing. I couldn't wrap my head around the bar angle making it that different than a stock type arm with good poly bushings.

 

I guess the part gathering has started, slowly. Pulled the trigger on some used just flowed and checked deka 60s! They may have to be upgraded at some point but they should get me started.

 

Heims/spherical joints aren't the answer to bind either. When the axle travels up and down; the control arms try to lengthen and shorten. This is why Ford used rubber bushings. They stretch and are compliant. Just a little education I received from Jack Hidley. Arms with heims on each end are hard on torque boxes but to a lesser degree, thus the popularity of torque box reinforcement kits.

 

Well... I don't know about that. I think they are the answer within the envelope that the car would normally operated within. I've personally done this, Put car on stands, remove springs from rear, and move housing around. With all spherical ends, the rear end moves around freely. You don't get any bind until you're way way out of whack, like drooping it 14" or more. In the range that it would normally operate, it's very free to move up and down and twist side to side.

 

Here's how Jack explains it:



"The easiest way to understand why the control arms must change length (in any 4-link that does not have equal length control arms which are also parallel) is this.



Look at the car in the side view. The upper and lower control arms on each side of the car each form two sides of a quadrilateral. As the rear suspension rolls, the angles in each quadrilateral on each side of the car changes. When this happens, the angle of the vertical line of each quadrilateral at the axle housing (formed by the UCA pivot and RLCA pivot at that end) changes. On one side of the car, the angle of that line tilts forward. On the other side of the car, the line on that side of the car tilts rearwards. This means that the axle tube on each side of the car is rotating in OPPOSITE directions as the rear suspension rolls. Essentially the 2.88” rear axle tube has become a giant rear swaybar. Either the tubes twists, the press fit into the center section spins, the control arms change length, the UCA mounts tear off of the car or some combination of all of this happens. This is why drag race cars spin axle tubes in the center section. It has nothing to do with how hard the car launches. It is mostly a function of the overconstrained rear suspension that they use.



If the car uses a parallel 4-link suspension with equal length control arms, as the rear suspension rolls, the lines on each side of the car do not change angle, because the control arms form the sides of parallelograms on each side of the car, so the control arms aren’t forced to change length."

 

Ok. I'm gonna disagree with a lot of what Jack says there. That's fine. I can admit that I don't know Jack.

 

He owns Maximum Motorsports. He is a suspension genius. If you Google the offset 3 link; it's really interesting. Chevy implemented it on production vehicles in the 50's I believe.

 

I am still in buying parts mode. Turbo showed up yesterday. If you have 8 mins of you life that you don't want to ever get back:

I did install the 3bar map sensor I got from EFI source. I need to work on the tune (start over)
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I am going to install coil overs. I was going to install an old set of 70/30 that were given to me years ago. The coil overs will not fit over the top of the struts. I have heard some drill out the welds? Is that safe? The car currently has kyb agx I could reuse them they have a small top.

What would you do. I don't want to by new struts.

 

I know you don't want to buy new struts but the Strange struts and coilover kits are tried and proven. I wouldn't mix and match products personally as far as coilover fitment.

 

Or....torque boxes fail because the axle naturally tries, and does rotate within the chassis. The upper control arms are pulling downward and towards the rear of the car. The lower control arms are being shoved upward and forwards, this coupled with a little bit of body roll........Foxbody control arms are bolted to nothing more than thin pieces of sheetmetal. Those pieces are then spot welded to other pieces of thin sheetmetal, Somethings gonna break. No need to try and be scientific and talk about imaginary lines.

The heims dont change the fact that the control arm is still pushing or pulling on its mounting area, but instead allows the control arm to slightly rotate during body roll. The heims end rotates relieving stress from the actual torque box.

 

Oh Boy, I was going to stay out of the rodends vs bushings but there is a lot of wrong info being posted so time to set things going on a correct path and I posted pics to help visualize.
Non-parallel 4-link systems angle the UCA's outward to help locate the rearend side-side. Doing so also causes the UCA to bind as the suspension move's up/down.
1. As the rearend moves DOWN in the chassis the UCA's try to get closer together at the torque box end but the torque box keeps them spread apart so there is binding.
2. As the rearend moves UP in the chassis the UCA's try and spread apart at the torque box.

I order to prevent the sheetmetal from flexing/cracking there needs to be soft bushings to allow flexing. When adding stiff poly bushings some of this flexing may be transmitted to the sheet metal so the sheetmetal/torque boxes may flex.

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In addition to the above the control arms themselves try to TWIST but again the torque box bolts limit this result thus more binding.

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Spherical rodends eliminate ALL the binding mentioned above.
ks

 

So was I partially wrong?

 

Yes spherical rod ends on all 4 arms = 8 pivots will correct the binding issues but they are not that street friendly. For a little more street friendly rod end look into a Johnny joint. They can be lubed plus rebuilt fairly cheap.

 

Yes, remove those big disks spot welded on the top. Be careful, you can destroy the strut. I have extensive field experience with destroying struts trying to get these off. lol.

 

Kevin is correct and I was definitely confused. (Nothing new!) Lol. Thanks for clearing this up; Kevin. Great reply!